Hi Josh,

The only benefit, from the info supplied, of using NaOH to maintain a high
pH would be if the water being used is recycled and the pH is considerably
low, or the water supply has a low pH.

I doubt whether there is any cost benefits with using NaOH, and
additionally the carbonate concentration should be about 1% for most if not
all dry film photo-resist developing; a solution within the 1% range
should maintain a sufficiently high pH for developing.

NaOH will tend to strip your exposed film and lead to opens in the
circuits.
You should consider using a proprietary developing solution that has a
buffering system.

Good Luck,
Lenny Kurup
On Sat, 4 Oct 1997 [log in to unmask] wrote:

> Recently, I heard of a dry film photoresist developer system that uses sodium
> hydroxide as a pH stabilizer.  Apparently, the system doses the developer
> sump with  carbonate based on a panel counter,  and sodium hydroxide based on
> solution pH.  The sodium hydroxide is used straight out of the drum, probably
> at around 40 % strength.    I'm told this controls pH in a very tight range,
> and reduces consumption of carbonate.
>
> I have some questions regarding a system of this type.
>
> 1.  What would the advantage be of using both chemicals?  Cost savings don't
> seem to be too likely, since you are replacing one chemical with another.
>
> 2.  What are the potential dangers of using sodium hydroxide in a developer?
>  What effects could it have on photoresist?
>
> 3.  Does the addition of sodium hydroxide cause bicarbonate to be converted
> to carbonate?
>
> 4.  How many people are using this type of system in production?
>
> Thank you in advance for your assistance.
>
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